Abstract: In order to understand the basic biology characteristics and dietary characteristics of  main economic species caught by the Chinese light-purse seine and light lift net fishery, this paper studied the biological characteristics such as sex and feeding level of chub mackerel (Scomber japonicas), based on the biological data of S. japonicas which collected in fishing vessels in Northwest Pacific Ocean high seas from Oct. to Nov. in 2016 and Apr. to Nov. in 2017. The results showed that the diet of S. japonicas in Northwest Pacific Ocean included 9 taxa (such as shrimps, fishes, copepods) and 16 subgroups of prey species. Shrimps were the dominated prey and Euhausiacea sp. was the most dominated one. The weight percentage (W) of fish prey was relatively higher than that of shrimps, however its numeric percentage value (N) was lower than the half value of shrimps. There was more species in the stomach of S. japonicas in summer and autumn than those in winter and spring. But it varied in  different seasons. There was no significant changes in feeding intensity and stomach fullness index (P) of chub mackerel with fork length less than 300 mm or body weight less than 300 g. However the feeding level and stomach fullness index  of chub mackerels tended to increase with their body size or weight in which with the fork length more than 300 mm or the weight more than 300 g. S. japonicas with the fork length more than 300 mm have lower trophic niche than that with the fork length less than 300 mm, because it feed more large bait. This study provided a basic data for the management and sustainable development of chub mackerel resources in the Northwest Pacific.

Key words: high seas in Northwest Pacific, Scomber japonicas, stomach contains, food characteristics, trophic level

摘要： 为了解我国公海灯光围网渔业开发现状及其主要渔获经济品种的基础生物学及其食性特征，根据2016年8—11月及2017年4—11月在西北太平洋公海生产船取样的日本鲭（Scomber japonicus）基础生物学现场测定数据，对其食性特征、摄食等级、生态位宽度等进行研究。结果表明，西北太平洋日本鲭主要摄食虾类、鱼类和桡足类等9大类16小类饵料生物，其中，虾类是最重要的饵料种类，以磷虾类最多；鱼类以未定种鱼类和远东拟沙丁鱼（Sardinops sagax）为主，鱼类饵料的质量百分比（W）比虾类高，但数量比例（N）不及虾类一半。日本鲭在夏、秋季比冬、春季胃含物种类的丰富度、摄食等级相对更高，具有一定的季节性变化。叉长小于300 mm或体质量小于300 g的日本鲭摄食强度与胃饱满指数（P）无明显变化；叉长大于300 mm或体质量大于300 g时，摄食等级与胃饱满指数均随体长或体质量增大呈现增大趋势；叉长大于300 mm的日本鲭由于摄食更多大型饵料，生态位宽度比叉长小于300mm的日本鲭普遍低。结果为今后西北太平洋日本鲭渔业的资源管理及可持续开发提供基础依据。

关键词: 西北太平洋公海, 日本鲭, 胃含物, 食性特征, 摄食等级